Conveyor belts are supported and driven by pulleys. Some pulleys are drive pulleys while others are idler pulleys or support pulleys. In order to reduce belt wear and to provide good traction between the pulleys and the belt, the pulley surface is covered with lagging, which is usually elastomeric material applied to the cylindrical surface of the pulley. Lagging increases belt life by eliminating slippage and it can be employed to promote belt alignment.
Originally rubber lagging was bonded to the face of the pulley. A pulley needing its lagging replaced was taken out of service and subjected to a process where old lagging was stripped from the face of the pulley and new lagging bonded to it. Lagging in the form of tires was developed so that the stripping and bonding process could be avoided by forcing a tire around the face of the pulley that fit tightly enough so that it would not slip with respect to the pulley face when it was in use. Whether using a bonding technique or a tire, it was necessary to take the pulley out of service, remove it from the conveyor system and replace it after new lagging had been installed. During the time lagging was being replaced the conveyor system was out of service.
Segmented lagging was latter developed. Segmented lagging involved a number of distinct lagging segments that could be attached to a pulley face by clamps or by welding. Segmented lagging was a great improvement because the lagging on a pulley face could be replaced without removing the pulley from the conveyor system or even removing the belt from the pulley. The portion of the pulley surface not in contact with a belt could have its old lagging removed and new lagging installed by replacing lagging segments one at a time. Segmented lagging is made by bonding elastomer to a metal plate and it is installed by connecting the metal plate to the pulley surface. U.S. Pat. No. 3,789,682 discloses such lagging segments and how they are attached to pulleys.
A preferred way of installing segmented lagging is to spot weld the metal plate portion of the lagging segment to the pulley face. However, the heat of welding can destroy the elastomer or the bond between the elastomer and the metal so it is necessary to have the metal plate extend far enough from the elastomer so that heat is dissipated between the point of the weld and the point of the elastomer bond to the metal plate. Generally, the metal must extend about 25 mm from the elastomer before welding can be accomplished without damaging the elastomer. Accordingly, two adjacent lagging segments attached to a pulley face by welding will have a 50 mm gap between the elastomer portions of the two adjacent segments. To eliminate belt wear and improve traction it is desirable to reduce the gap between the belt-contacting elastomer portions of adjacent lagging segments.
Another way to install lagging segments is to clip them to the face of the pulley as disclosed in U.S. Pat. No. 3,789,682. The portion of the lagging held between the clips and the pulley face is a portion of the metal plate extending beyond the elastomer part of the lagging and the distance between the elastomer portions of two adjacent lagging segments is twice the length of these extensions plus the space between them used by the clips. This distance is also at least 50 mm and this spacing also causes the problems mentioned above.